1. Field of the Invention
This invention relates to diamond studded insert drag bits.
More particularly, this invention relates to drag bits with a multiplicity of individual diamond faced tungsten carbide inserts mounted in the face of the drag bit with strategically located fluid coolant passages adjacent the inserts to constantly cool and clean each insert blank.
2. Description of the Prior Art
Most state of the art diamond drag bits are designed with the first consideration given to location of the individual diamond cutter inserts.
For example, U.S. Pat. No. 4,098,363 discloses a diamond drill bit employing spaced, shaped diamond cutter elements arranged in rows separated by large fluid channels. The channels are formed in the bit body and are utilized for bit cleaning and detritus removal action. A series of nozzles are randomly placed within the channels, the channels themselves distribute the fluid over the array of diamond cutters. This type of bit is normally fabricated from a material which is highly resistant to erosion, especially where fluid channels are provided in the face of the bit. The diamond drill bit just described is cast from expensive carbide material with the waterway channels formed therein to provide an erosion resistant base for the bit body.
This patent is disadvantaged in that fluid flowing in the channels positioned nearest the center of the bit flows at a higher velocity than the fluid flowing through channels positioned radilly outwardly from the center resulting in a non-uniform flow velocity condition. Also the fluid volume passing individual cutters or pairs of cutters is not uniform.
The diamond studded insert drag bit of the present invention is relatively flat-faced with multiple fluid channels formed in the face of the bit. The diamond insert blanks are so positioned to most effectively advance the bit in the borehole. The fluid passages are strategically located adjacent the inserts to provide uniform flow and a relatively even pressure drop over the entire face of the bit as well as cool and clean the individual inserts. No special materials or coolant passage channels are necessary to achieve these parameters.
The fluid passages are simple openings or holes to admit fluid through the bit as opposed to nozzle bodies that serve to accelerate the fluid out of the nozzle. Since the fluid flow is more constant because of the strategic hole locations, a more uniform velocity distribution across the face of the bit results. Since fluid flow is constant and exit velocities are lower, bit erosion is minimal. Therefore, the bit body need not be cast from expensive carbide material and complicated channel waterways are unnecessary. The instant invention teaches the fabrication of diamond studded insert drag bits from machined alloy steel.